Introduction to Archaeology: Class 9

ã Copyright Bruce Owen 2002

• Finding sites: survey methods
• archaeologists usually find or confirm sites by recognizing artifacts on the surface
• sometimes walls, foundations, or mounds of accumulated debris are visible
• more often, bits of broken pottery or stone tools are scattered on the surface
• more details on this later...
• many sites are obvious or were never lost
• hard to miss the pyramids, Roman coliseum, etc.
• asking the local people
• they often know where they have found artifacts while plowing fields, digging wells, etc.
• they may have oral traditions of where events occurred in the distant past
• old maps and documents
• placenames
• air and satellite photos
• may show subtle patterns in relief
• soil color
• plant growth, etc.
• accidental discovery
• such as when a bulldozer working on a construction project plows up some artifacts
• very common; many important sites have been found this way
• The most thorough method is systematic site survey
• walking in an orderly pattern back and forth across the landscape and recording all artifacts that are laying on the ground
• If there is ground cover or sites are likely to be buried, it may be necessary to dig small trenches in likely areas, bore holes with augers, etc.
• Systematic survey is slow and expensive
• but unlike the other methods, it can give you a more complete, relatively unbiased picture of the distribution of sites in the whole region
• not just the places that happen to have standing architecture, be remembered, have been discovered accidentally, etc.
• Thomas emphasizes looking for particular sites - a cave that will answer his questions, or a specific historical mission
• But often we just want to know what is there in general, rather than find a specific site
• Or we want to look at the settlement pattern: the pattern of distribution of sites of different types across the landscape, and their relationships to natural resources and each other
• The settlement pattern of a given region and time can tell us a lot about the culture that produced it - often things that would be difficult or impossible to learn from excavating a single site
• simply finding surface evidence of sites, recording what is there and where, can provide a huge amount of information for much less effort and cost than excavation
• 100% coverage (or "full coverage") survey methods
• line of archaeologists walking across the countryside, looking at the ground
• spacing within the line and between passes determines the largest possible site that could be missed
• collect standardized information about each place where any evidence is found
• field forms
• location, site number or name, how to find it if necessary
• description of sherds, lithics, walls, etc. found
• size of surface scatter of artifacts; map of the area covered or any architecture
• description of the place: location, topography, ecology, access to water, travel routes, view, etc.
• surface collections
• "grab sample": purposefully collected items that seem interesting or diagnostic
• "systematic sample": collection made by systematic rules. For example:
• Draw a 2 meter diameter circle on the surface near the center of the scatter, using two large nails tied together by a 1 meter string
• Pick up every sherd within the circle that is larger than 3/4" square
• and/or every stone tool or flake of stone tool material larger than 1/2" square; or whatever
• These are taken back to the lab, categorized, cataloged, and used to date and otherwise characterize the site
• some environments where you can't see the ground due to plant cover or where artifacts are typically below the surface may require:
• periodic shovel tests, post-hole samples, or auger samples
• periodic clearing using a machete, etc.
• this is VERY slow and expensive to do over a whole landscape
• Sampling strategies
• if it would be too slow or expensive to cover the whole landscape, some kinds of questions can be answered by studying just a sample of the area
• like a series of 100 x 100 meter areas scattered across the landscape
• this could help with questions like:
• what is the general density of different kinds of sites?
• what are the common kinds of sites, and what are the rare ones?
• what kinds of areas are sites typically found in?
• near lakes, on hilltops, or in meadows?
• this could tell you a lot about the subsistence practices of the people who lived at the sites
• or their need for defense, etc.
• are certain kinds of sites found only in certain parts of the region?
• did the red-pottery people live to the south and the white-pottery people to the north, or were both types of pottery used throughout the whole region?
• this could tell you about ethnic groups, political relations, economic activities, etc.
• judgement samples
• sample areas are chosen to test areas of interest
• like: one area on the shore of each lake; one on each hilltop; etc.
• this may introduce biases into the data
• sites in areas that the investigator does not think are worth checking will never be found - his assumption will never be disproved
• the resulting data does not accurately represent the region as a whole
• you couldn't say things like "there are 2 sites per square kilometer", because you have only looked in certain places; who knows what the site density is in other places?
• systematic samples
• sample areas are selected in some regular pattern
• like 100 x 100 meter square areas arranged in a 1000 meter grid
• this would be a 1% sample of the area
• probably a bit small for most purposes, but a start
• this is less biased, but could still have problems.
• say sites tended to be about a kilometer apart.
• with luck, you might hit every site, and think the site density was very high
• or the sample areas might fall in between them, and you would think the site density was very low
• random sampling
• sample areas are selected using a random number table, random number generator on a computer or calculator, etc.
• should avoid introducing any systematic biases into the data
• all parts of the region are equally likely to be sampled
• spatial patterning of site locations will not affect how likely sites are to be found
• the final data is a fair representation of the whole region
• stratified random sampling
• but why waste lots of time looking in the unlikely areas where you never find anything?
• or why risk missing certain parts of the region completely?
• say only 0.1% of the region is riverbanks, but you think people probably liked to live along riverbanks
• a random 5% sample might well not include a single survey area that falls on a riverbank
• solution: stratified random sampling
• divide up the region into a few kinds of terrain, like "exposed bedrock", "hillsides", and "riverbanks"
• these are the "sampling strata"
• then do a random sample within each stratum
• this assures that you cover some of each
• you can even do a higher percentage sample in the more promising areas
• say, just 1% coverage of the exposed bedrock areas
• but 10% coverage of the riverbank areas
• this gives you a truly representative, unbiased sample of each kind of area
• you can extrapolate this to the entire area by multiplying by the area of each stratum
• say you find 0.1 site per square kilometer in the exposed bedrock sampling stratum
• 1 site per square kilometer in the hillside stratum
• 10 sites per square kilometer in the riverbank stratum
• to estimate the total number of sites in the region, you use a map to measure how many km² each stratum occupies
• then multiply the site density in each by the area of each
• this gives you an unbiased estimate for the whole region without having to cover too much exposed bedrock...
• transects
• but random sampling areas are often hard to get to; they require lots of wasted travel time
• alternative: transects
• transects are sampling units in the form of long strips
• the strips typically cross a variety of terrain types
• so they tend to give a fairly representative sample of the landscape
• but they are easier to cover without a lot of wasted travel time
• transects are not really random and unbiased, but they are a fair approximation
• these same sampling strategies will be useful in laying out surface collection units on large sites, selecting spots to excavate, etc.
• problems with sampling:
• by definition, you only get data about part of the area
• most of the area is never covered
• so, rare or unique types of sites can easily be missed
• if you did a random sample survey of lower Egypt, odds are high that you would miss the great pyramids... and that would certainly mess up your conclusions.
• also, you don't get the whole pattern, just little pieces of it
• so a sampling scheme would tend to hide spatial patterns like:
• sites were located in lines along rows or canals
• sites arranged with a few large sites, each surrounded by a halo of small sites
• patterns like these could be very useful for reconstructing social organization - but sampling techniques rarely reveal them
• Settlement pattern analysis
• generally works best with 100% coverage, so patterns can be seen
• Gross patterning: what kinds of sites are where?
• are there sub-regions associated with different kinds of sites (farming villages vs. hunting camps; different ethnic groups, etc.)?
• did the preferred locations of sites shift over time?
• due to changing environment? economic specializations like fishing vs. farming? building of canals? etc.
• did overall population rise, fall, or remain constant?
• are sites associated with certain artificial features, like roads or canals?
• this can help to date otherwise enigmatic features
• and to suggest what they were for
• this level of settlement pattern analysis can often work with sampled data
• Catchment analysis: what resources were sites located near?
• simply draw a circle of "x" km radius around each site on a map that shows ecological zones or other distributions of resources
• measure the area of each kind of resource zone within the given distance from the site
• this gives a rough idea of what resources were probably important to the people at the site
• slightly better way:
• draw the boundaries according to walking time, rather than simple distance
• some terrain may be harder to cross, or there may be natural barriers like rivers or cliffs
• what if the circles intersect (as they probably will, unless the region is seriously underpopulated)?
• use Thiessen polygons: a way of dividing up the landscape into areas that probably "belonged to" each site
• simplest way:
• draw lines connected each site to every other nearby site
• draw a perpendicular line bisecting each of the connecting lines
• these form polygons such that the area within each is closer to the site in the polygon's center than to any other site
• slightly more sophisticated way:
• estimate the size or population of each site
• rather than bisecting the connecting lines, divide the connecting line proportionally to the size or area of the sites (farther away from bigger sites, closer to smaller sites)
• there are computer programs for doing this sort of work
• Site size hierarchies: do site sizes reveal something about political organization?
• sites all the same size would suggest an unspecialized society in which all settlements had similar functions
• a few large sites and many small ones would suggest that the large sites might have had some additional functions that the small ones didn't
• like a temple, royal palace, marketplace, craft workshops, etc.
• even without any other information, such a pattern of site sizes suggests a more complex social, political, and/or economic organization
• usually presented as a "rank-size" graph
• with site size on the vertical axis (usually logarithmic)
• and site size "rank" on the horizontal axis (that is, first on the left is the largest site, next is the second largest, etc.
• the shape of the curve that this forms gives an idea of the distribution of site sizes
• a steep drop from a single very large site is a "primate site size hierarchy": one big capital-like site, probably a highly centralized, strongly administered society
• etc.
• Nearest neighbor analysis: a statistical analysis that gives an estimate of the randomness of site locations
• why on earth would that be useful?
• the assumption is that natural resources are more or less randomly distributed, or are evenly distributed
• so if sites are randomly distributed, their locations are not affected much by the locations of other sites
• so social interactions between sites, competition, administration, etc. were not very important in determining their locations
• but if sites are very non-randomly distributed, that means that the average distances between them tend to be somewhat regular
• that is, the location of one site is partially determined by the location of others
• what could cause that?
• competition: the sites are evenly spread out to maximize the area each has access to and minimize closeness to others
• administrative needs: sites are neither too close (which would waste administrative resources due to duplication) nor too far apart (which would stretch lines of communication and make administration more difficult)
• trade: sites are neither too close (not enough market for their goods) nor too far apart (excessive transport costs for goods)
• Analysis based on Central Place Theory: looks for patterns of administrative or economic centers spaced widely apart, each surrounded by smaller sites dependent upon them
• ideally in roughly hexagonal patterns - but this would only be so on the proverbial "featureless plain", never in reality
• may have more than two levels of site types
• if there is such a pattern, it indicates even more complex, centralized administration or exchange
• and there are many other more specialized approaches
• Point: from just in the spatial patterning of sites and the small amounts of material on the surface, one can figure out a lot about past societies